From Coastal Flooding to Residual Beach Functionality: Implications of Sea-Level Rise for Coastal Management in Southern Spain

Sea-level rise may substantially reduce the dry space available on sandy beaches, although its effects depend strongly on local beach characteristics. This study evaluates the residual spatial functionality of five beaches in southern Spain using two normalized indicators: residual available surface area (FA) and residual available beach width (FW). Both express the proportion of dry beach space remaining relative to a common present-day reference condition without wave run-up. The analysis builds on previously calculated inundation results for present conditions and Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 scenarios for 2026–2045 and 2081–2100, including astronomical tide, meteorological residual, sea-level rise, and wave run-up. Marked differences are observed among the studied beaches across both time periods. Under RCP 4.5 in 2026–2045, Torreguadiaro retains 85.1% of its reference area and 79.8% of its reference mean width. Rinconcillo retains 31.9% and 38.7%, respectively. Under RCP 8.5 in 2081–2100, these values decrease to 75.6% and 65.3% at Torreguadiaro. At Rinconcillo, they decrease to 7.1% and 17.6%. FA and FW also evolve differently among sites: their values remain relatively close at Malagueta but diverge markedly at Rinconcillo under the most severe scenario. Joint consideration of FA and FW therefore provides complementary information on the amount and configuration of residual dry beach space and may support comparison among beaches from a coastal management perspective.